Only REAL difference was the modems. AT&T issued a Motorola Netopia modem, the local ISP a brand I had never previously heard of, TP-Link. After dropping AT&T DSL, they never asked for their modem back. Reset it to factory default, put in settings for the local ISP, no more lag or buffering video when loading pages, even though both modems were hooked to my Netgear router.
Made a trip today, bought a Motorola DSL modem/router combo unit. Set it up to work with the local ISP. Still no lag. Returning the craptastic TP-Link to the ISP soon, will save $5/month lease fee! Didn't want to rely on the 5 year old AT&T supplied modem, it could fail any time given the age of the thing!
Local ISP techs kept chalking the lag up to amount of bandwidth consumed at any given time, although usage was the same under AT&T. Took ME to finally conclude that it was the crappy TP-Link modems. Unless they test it themeslves, they'll NEVER believe me however, since I have no "real" tech training!